Method and apparatus for dermatology treatment

ABSTRACT

A laser treatment method is provided which removes vascular and pigmented lesions from the skin of a living human. The methodology involves a carefully designed treatment protocol utilizing a modified optical apparatus. The apparatus is a modified diode laser system, designed for optimal therapeutic selectivity.

RELATED APPLICATIONS

This application claims the benefit of the commonly-owned provisionalapplication Ser. No. 60/001,077, filed on Jul. 12, 1995 for "METHOD ANDAPPARATUS FOR PARAMETERS FOR LASER MEDICAL PROCEDURE" and is acontinuation-in-part of the commonly-owned U.S. patent application Ser.No. 08/546,791, filed on Oct. 23, 1995, now U.S. Pat. No. 5,658,323.

FIELD OF THE INVENTION

The present invention is directed to the removal of vascular and otherpigmented lesions from the skin utilizing a modified high power diodelaser system under carefully controlled conditions.

BACKGROUND

Human skin may contain a range of abnormalities including vascular andpigmented lesions. Although not always dangerous to the individual, suchabnormalities are frequently cosmetically troublesome.

Vascular lesions, in particular, may take several manifestations. Commonexamples are `port wine` stain birthmarks; telangiectasias (spots orvessel lines formed by dilated capillaries or other small bloodvessels); and hemangiomas (benign tumors composed of well-formed bloodvessels). Pigmented lesions generally consist of hyperactive melanocyteswhich produce a local overabundance of melanin.

Leg telangiectasia, or `leg veins`, are chronically dilated bloodvessels visually apparent as red or blue linear or `spider` structures.They may cover extensive or local areas of the leg and are more commonin women. Large diameter vessels may cause discomfort, while smallerdiameter vessels are more often considered cosmetically unsightly bypatients.

Up to 80 million adults in the United States alone are affected by legveins. It is estimated that 29-41% of women and 6-15% of men worldwidehave `abnormal` (visually apparent) leg veins. Most vessels presentingfor treatment are less than 1 mm in diameter although candidates fortreatment have diameters up to 3 mm.

The vessels consist of dilated blood channels in an otherwise normaldermal stroma. The blood channels have a single endothelial cell liningwith thickened walls consisting of collagen and muscle fibers.Clinically, these vessels may be categorized as linear, arborizing,spider or papular.

Such dilated vessels may result from pregnancy or the use ofprogestational agents. A genetic link is usually also present. Some suchveins are associated with a high pressure flow from a feeding reticularor varicose vein.

In order to eradicate a leg vein, it is usual to damage the endothelialvessel lining or surgically ligate the vessels. Such surgery is radicaland performed on an in-patient basis. Endothelial damage may be inducedby means of Sclerotherapy or by the use of light energy on an outpatientbasis.

Sclerotherapy is currently the favored method of non-surgical leg veineradication.

Sclerosing agents have traditionally been employed to damage endothelialcells. Such agents as sodium tetradecyl sulfate, hypertonic saline andpolidocanol are injected into large vessels (>1 mm in diameter) andresult in death of the endothelium. Several systemic injections to a`feeder` vessel system may result in widespread death of the ectaticvessels.

The use of sclerosing agents is associated with telangiectatic matting(formation of clusters of small vessels) in 35% of patients treated, andwith hyperpigmentation (residual brown pigmentary staining) in up to 30%of vessels treated. Other adverse sequelae are possible, includingulceration, edema (blistering) and systemic anaphylactic shock. Vesselrecurrence within 5 years has been observed in up to 40% of patientsstudied. Further, many patients are fearful and resistant to the use ofneedles.

Hyperpigmentation pursuant to sclerotherapy is particularly troublesome,as it replaces the blue vessels with a brown discoloration which maypersist for up to 5 years. This effect results from the catabolism ofextravasated blood to hemosiderin, a form of iron deposition, brown incolor, which may reside in the proximal dermis for up to 6 months.

Sclerotherapy injection difficulties render sclerotherapy relativelyunsuitable for the routine treatment of vessels with diameters of lessthan 1.0 mm and for the treatment of many larger vessels with diameterin the range 1.0-3.0 mm.

Light energy has been utilized for the treatment of cutaneousvasculature.

When use of light is under consideration, one can choose to varywavelength, pulsewidth or coherence (uniformity). Wavelength willtypically be chosen by consideration of the absorption and scatteringcharacteristics of the target tissue layers. The absorptioncharacteristics are typified by several peaks in the visible region ofthe spectrum, due to target chromophores, together with a monotonicdecrease into the infra-red region. The scattering of tissue decreasesmonotonically through the visible to the near infra-red region andbeyond.

Both coherent laser light and incoherent light from a flashlamp-typesource offer the potential for high selectivity of treatment. Shortwavelength (<500 nm) light is usually not employed, since it is highlyscattered in tissue and therefore unable to penetrate to a sufficientdepth. Light of a wavelength greater than 500 nm has been employed forthe treatment of vascular lesions. The absorption profile of whole bloodis shown in FIG. 1. This profile will vary with anatomical location,since blood constitution varies, but can be taken as generallyrepresentative.

Vascular diseases characterised by small vessels such as the Port WineStain respond well to visible wavelength pulsed laser light from apulsed dye laser, typically with a wavelength in the 550-600 nm range,which is tuned to a local absorption peak of the intra-vascular blood.Such light, which is absorbed in the top 0.05 mm of the vessel, cancoagulate and thereby thrombose a significant portion of the entirecross section of small vessels (<0.1 mm). Construction of such a pulseddye laser for dermatology applications has been described previously.

Visible wavelength laser light is less effective on larger diametervessels (>0.1 mm). The main reason for this is that it is too highlyabsorbed in blood. Although vessel rupture is possible, this representsa non-optimal mechanism associated with the involvement of only thesuperficial portion of the vessel, due to the shallow absorption depthof the light. Regrowth of the insufficiently damaged vessels usuallyoccurs under these circumstances. Also, the rupture of the vessel leadsto an unsightly post-treatment purpura (`bruising) which can persist forup to 2 weeks. This is not well tolerated by patients.

It should be remembered also that dilated vasculature of the extremitiesis also associated with a different and variable ratio ofoxy/deoxygenated hemoglobin, the main absorbing chromophores within theblood. Different considerations are then pertinent in devising anappropriate therapeutic regime. A typical leg vein is characterised by arelatively low oxygenation of around 70%, responsible for an occasionalblue `hue` in some vessels. (Hemoglobin, as typically found in port winestains on the face, is bright red in color and usually approximates aconstant 95-100% oxygenation level). The near infra-red absorptioncharacteristics of the two hemoglobin types which dominate bloodabsorption are shown in FIG. 2. Both hemoglobin types have equalabsorption around 800 nm, rendering absorption independent ofchromophore mix (and hence of anatomical location) at this wavelength.This provides a useful insensitivity to anatomical location andindividual characteristics in terms of precise level of oxygenation. Themagnitude of the absorption coefficient around 810 nm is well suited tothe dimensions of the target vessels. Light at this wavelength isabsorbed in a 2 mm blood layer, as opposed to light in the historicallyemployed 500-600 nm region, which is absorbed in a blood thickness ofless than 200 μm.

Short wavelengths are also highly scattered as they pass through theturbid dermis to reach the target vessels. An increase in scattering ofmore than 50% occurs as wavelength is shortened from the near infra-redto the mid-visible. This renders light in the 500-600 nm region lesssuited to the targeting of deeper dermal vessels.

A further disadvantage associated with existing short wavelengthcoherent laser sources such as the pulsed dye laser is their shortpulsewidth. With a maximum around 1.5 milliseconds, no time forconcurrent conduction of the heat is permitted. Further, such anexposure interval is better suited to the thermal relaxation timeconstants of overlying melanocytes, leading to unwanted temperature riseand the possibility of damage. Such melanocytes have thermal relaxationtime constants in the range 100-300 μsecs, and would retain significantthermal energy within a 1.5 millisecond exposure. An availablepulsewidth of up to several tens of milliseconds would be desirable andwould obviate this effect.

Also, the high cost and the significant bulk of the componentryassociated with short wavelength (500-600 nm) coherent light sources areprohibitive factors.

A broadband-emitting incoherent flashlamp light source has beensuggested to offer an alternative approach for the treatment of legveins. Such a source may utilize a spread of principally infra-redwavelengths (550-1200 nm) most of which exhibit a smaller degree ofabsorption better suited to larger vessels. A longer pulsewidth of up to100 milliseconds is also available, permitting concurrent heatconduction through the vessel and beyond to a radius of up to 250 μm. Asa consequence, the full volume of the vessels may be affected, asrequired for vascular necrosis, although significant perivascularnecrosis may result.

Clinical results from the use of this class of source are at thepreliminary stage and may include a reduction of the hyperpigmentationassociated with the shorter wavelength/pulsewidth dye laser sinceproximal rupture is no longer the mechanism in effect. Adverse effectsinclude the occurrence of gross heating effects, edema and blisteringassociated with the incoherent light, since incoherent light has poorpenetration characteristics in human tissue. Also, the broad mix ofwavelengths includes spectral regions which are less suited to thelesion characteristics, such as the 1000-1200 nm region, which displayslittle vascular selectivity.

Further, such a system is physically clumsy and difficult to use.

Such an incoherent light cannot be easily focused to a spot size whichefficiently overlaps the vessels and hence unaffected tissue is involvedin the pathological effects.

The above disadvantages, taken together, limit the applicability of thistechnology.

Another manifestation of the incoherent flashlamp based light sourcerelates to the use of a mercury-xenon vapor lamp, with specific emissionpeaks in the visible portion of the spectrum. This incoherent sourcewill often result in gross heating of proximal tissue, with a resultantneed for concurrent cooling of the skin. Further, the visible emissionspectrum of the lamp lends its use to small vessels found in Port WineStains, since the light will be absorbed in the top 0.05 mm of thevessels. Larger leg veins are not cited in the patent for this devicefor this reason.

FIG. 3 illustrates graphically the effect of tuned visible (˜580 nm) andnear infra-red (700-900 nm) coherent light on small (<0.1 mm) andmoderate (0.1 mm<diameter<1.0 mm) sized vessels. This figure illustratesthe inherent suitability of visible band light to small vessels and ofinfra-red band light to moderately sized vessels, since destruction of asignificant proportion of the vessel is required. This suitability isfully harnessed only if pulse widths of the order of several tens ofmilliseconds are available, with their concurrent conduction permittinguseful proximal vessel wall damage. In particular, the aforementionedpulsewidth of 1.5 milliseconds likely will not permit sufficientconduction of heat to guarantee vascular elimination, since a radius ofonly 30 μm is reached in this time. Such a short pulsewidth will furtherthreaten the overlying epidermal layer. Also, extravasation andsecondary purpura and hyperpigmentation are likely since efficientcoagulation of the intravascular blood and extravascular tissue rim isnot attained.

While such short pulses may be appropriate for very small vessels (<100μm) which lose heat rapidly, larger vessels are likely to requireproportionately longer exposures. Vessels with size in the range 100-500μm may require exposure time intervals of 1.5-40 milliseconds, whilevessels larger than 500 μm may require exposure time intervals of1.5-100 milliseconds.

In FIG. 3, the shading shows the heat generation during the pulseresulting from direct absorption. The denser shading associated withvisible light signifies the attainment of high localized temperatureswith associated explosive effects. This heat can be expected to conductfurther to affect a peri-vascular tissue volume if sufficiently longpulse widths are employed.

A near infra-red narrow-band coherent laser light source with variablepulsewidth would offer the potential for more thorough coagulation oflarger vessels, without the adverse effects attendant with the flashlampsource. Such a source intentionally employs wavelengths which exhibitlower blood specificity, contrary to traditional approaches wheremaximum specificity is sought. Further, such a source would betterpenetrate to the required depth in tissue than do visible lightwavelengths or incoherent infra-red wavelengths, since opticalscattering is comensurately reduced. An alternative source of nearinfra-red light and associated treatment method is described in thefollowing sections.

SUMMARY OF THE INVENTION

The present invention comprises a laser treatment method and apparatusfor the removal of vascular and other pigmented lesions from the skin.

The treatment method, according to one embodiment of the invention,includes:

Irradiation of the skin with power level in the range 10-500 Watts,pulsewidth 1-99 milliseconds, and spot size 0.5-10.0 mm with coherentpulsed light with wavelength in the range 700-1000 nm,

controlling the applied radiation such that desired endpoints areobserved during treatment, consisting of mild `blanching` withoutsignificant pigmentary or textural change,

allowing the skin to heal for a period of 2-16 weeks,

irradiating on 0-5 subsequent occasions with additional exposures,

One apparatus for practicing the foregoing embodiment consists of:

a modified high power semiconductor diode laser system with pulsewidthvariable from 1-99 milliseconds.

The invention incorporates a modified laser apparatus with newapplication, together with a novel treatment method for the eradicationof leg veins. The new treatment thus developed presents the potentialfor numerous significant clinical and practical advantages. Clinicaladvantages include a reduction of unwanted purpura associated withextravasation and to minimization of associated secondaryhyperpigmentation. Enhanced clearance will also result from theoptimization of wavelength and pulsewidth in a coherent device able toattain significant penetration depth. Pigmented lesions may also betreated with pulses between 1-5 milliseconds. The clinical advantages ofthe invention are conferred by the use of a `detuned` coherent infra-redwavelength region and pulsewidth matched to the physical characteristicsof the target area. This development of a clinically effectivetherapeutic treatment using a carefully controlled modified laserapparatus with associated minimization of adverse effects is a majorimprovement and advance over current options. Other practical advantagesinclude the ease of use of the compact, portable and inexpensiveequipment.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference may be had to the following detailed description and theaccompanying drawing, in which:

FIG. 1 is a graph showing a typical absorption profile of whole blood;

FIG. 2 is a graph illustrating the near infra-red absorptioncharacteristics of two principal blood types;

FIG. 3 is a graph illustrating the effects of tuned visible light and ofnear infra-red coherent light on small and on moderate sized bloodvessels;

FIG. 4 is a graph indicating percentage of light absorption in a onemillimeter diameter blood vessel as a function of illuminating wavelength;

FIG. 5 is a graph illustrating water absorption in a blood vessel as afunction of illuminating wave length;

FIG. 6 is a graph illustrating the thermal effect of a diode laser pulseas a function of tissue depth; and

FIG. 7 is a block schematic representation of tissue treatment apparatusaccording to one practice of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Theoretical considerations

As discussed in the foregoing, it is first necessary to identify anoptimal wavelength and pulsewidth regime.

In terms of wavelength, a lower absorption coefficient than thoseexhibited in the visible spectral region is desirable to affect theentire volume of larger vessels. To fill a 1 mm diameter vessel, forexample, an absorption coefficient in the range 1-10 cm⁻¹ would beoptimal, as compared with the absorption coefficient at the yellowwavelength of 585 nm of 300 cm⁻¹. As shown in FIG. 2, the near infra-redwavelength range (700-1000 nm) presents absorption coefficients in thisrange. This graph illustrates the absorption characteristics of oxy anddeoxygenated hemoglobin, the dominant blood chromophores.

Although the absorption coefficient is significantly less in the nearinfra-red than that found in the yellow visible region, the thickness ofleg vessels is such that the incident energy is effectively utilizedthroughout the depth of the vessel. Hence, an equivalent proportion ofthe applied total energy may be absorbed in the vessel in each case,with greater uniformity of deposition for the near infra-red region.This effect, shown in FIG. 4, indicates that the specificity of actionis only ultimately lost for wavelengths above 1000 nm, where asignificant portion of the light passes through the vessel. In the530-900 nm spectral region, most of the light is utilized in a 1 mmvessel. For larger vessels in the range 1-2 mm, almost all of such lightwill be utilized. The precise selection of wavelength determines theuniformity of absorption of the light.

It is also important that tissue water absorption be minimized in orderthat maximum depth of penetration be attained. Water absorption, shownin FIG. 5, presents a peak at 980 nm and other peaks further into theinfra-red. To avoid this broad peak and operate at a reliable wavelengthfor the laser, a laser source emitting in the 800-850 nm range may beconsidered optimal. Water absorption at 810 nm, for example, may beconsidered negligible.

Melanin absorption, still significant at 810 nm, competes for absorptionof the light. Significant heating of the epidermis can be avoided by useof pulses or duration longer than several milliseconds. These ensureefficient conduction of the heat from the melanocyte during the pulsedexposure, since melanocytes have thermal relaxation time (time to losehalf of their heat) constants of less than 1 millisecond. By comparison,larger blood vessels, which better retain their heat, experience auseful temperature rise. Hence, specificity of vascular effect can beretained.

Conversely, melanocytes may be targeted by means of the use of shorterpulse widths, of around 1-3 milliseconds.

Selection of pulsewidth is of great importance in the precise definitionof extent and localization of damage. It is critical that the resultantheat production is unable to conduct widely into the surrounding dermis,since this would cause significant thermal tissue damage. It is howeverimportant that a partial conduction occurs. These considerations dictatethat the applied pulse duration of the energy be well matched to themechanical characteristics of the absorbing vessels. For a vessels withsize in the range 0.1-3.0 mm, a favorable pulsewidth regime is in therange 1-100 milliseconds, corresponding to a better approximation to the`thermal relaxation time constant` of the target (time for a vessel tolose half of its heat). In practice, the pulsewidth need not be as longas the thermal relaxation time, but must provide for sufficient lateralconduction to impact a significant perivascular rim of tissue. Sincesmaller vessels within the above range will more quickly lose theirheat, it may be necessary to more rapidly apply the energy to such.Hence, an ideal treatment regime for smaller vessels might use shorterexposure pulse widths within the 1-100 millisecond range than would anideal regime for larger vessels. This may produce some superficialheating since melanocytes will better retain their heat. Accordingly, aspulsewidth is shortened towards 1 millisecond, it may be appropriate toutilize adjunctive epidermal cooling.

Another useful variation of the treatment parameters involves theapplication of a number of shorter pulses within the pulse envelope,rather than a continuous longer exposure. This allows some vascularrelaxation during the exposure which may create better uniformity of theheating process.

To further validate this thought process, a computer technique known asMonte-Carlo modeling may be undertaken to simulate the effect of suchlaser light on leg veins. This intensive approach generates manymillions of optical events in the skin to ultimately derive opticalenergy distributions. In this modeling, a sample 0.5 mm thick bloodlayer was assumed at a 0.5 mm depth beneath a highly scatteringepidermal/dermal top layer. This model yields an optical distributionwhich may be converted to a thermal distribution by means of thecalculations below.

    §T=E/C×M

where

§T=temperature rise in small tissue segment

E=energy deposited in tissue segment=no. of photons×photon energy

C=specific heat capacity of tissue

M=mass of tissue segment.

Tissue parameters, such as scattering and absorption, as used in thismodel were obtained from the literature, although it should be notedthat no previous modeling work is evident which addresses the treatmentof leg veins in the wavelength region described here.

Various power and energy levels were used in the modeling. As anexample, FIG. 6 illustrates the thermal profile at the end of anexposure of 20 Watts of 800 nm laser light at this wavelength. Variousbeam spot sizes and pulse widths were modeled. In FIG. 6, a spot size of1 mm, combined with a pulsewidth of 30 milliseconds, were employed (notethat the blood vessel surface begins at a depth of 500 um). Thetemperatures shown are sustained in the blood vessel beyond the durationof the exposure (30 milliseconds), providing sufficient locallydeposited energy to kill the vessel. The thin epidermal layer loses heatmore rapidly and is thereby spared from gross damage for such a longpulsewidth. Minimal perivascular heating is expected for appropriatepulse durations (1-100 milliseconds).

This figure illustrates that, while light in the 800-850 nm region hasrelatively low absorption, a preferential effect on the vasculature maystill be induced.

From the above theoretical studies, it has become apparent that a lasersource emitting in the wavelength region 800-850 nm, with variablepulsewidth and spot size capabilities, will meet the conditions requiredfor optimal clinical treatment of a sample leg vessel with diameter of0.5 mm. The same principles apply to a range of vessel size between0.1-3.0 mm diameter. It is important that the source be a laser, withits attendant coherence, rather than an incoherent source such as, forinstance, a flashlamp-based source. Coherent light is unidirectional innature and better suited to penetration through turbulent human tissue.

In the modeling example cited above, as stated, a vessel of diameter 0.5mm at depth 0.5 mm was brought to damage threshold by means of a 20 Wattsource with 1.0 mm spot size, operating with a pulsewidth of 30milliseconds. To allow for deeper, thicker vessels, and for the use oflonger pulse widths and larger round and elliptical spot sizes up to 10mm, I have calculated that a peak power of up to 500 Watts may berequired. An associated pulsewidth in the range 1-99 milliseconds wouldbe required.

By means of the use of such an apparatus, adverse sequelae associatedwith currently available technologies will be reduced. In particular,purpura and post-treatment hyperpigmentation associated with mechanicalrupture and extra-vasation will be greatly reduced, as the longer pulsewidths produce a more uniform effect. Also, deeper penetration of thelong coherent 800 nm wavelength will improve treatment efficacy.

The above represents a summary of the theoretical considerationsemployed to calculate an appropriate parameter set. As part of thisinvention, an appropriate apparatus and treatment method were alsodevised.

Apparatus

It was determined after a review of the scientific literature, that somemanifestation of modified diode laser technology would be capable ofproviding the requisite parameter set.

Semiconductor diode laser technology, first developed in 1962, todayfinds application in devices ranging from consumer electronics andcommunications to medicine.

A basic system, in the high power configuration envisaged here, consistsof an electronic power supply coupled to a semiconductor crystalencapsulated in an optical chamber capable of capturing and harnessingoptical emissions from the crystal. When a large direct current ispassed through the crystal, optical emission is generated and amplified.A beam of light results, with a high degree of brightness anddirectionality.

The basic system is further refined by means of the addition ofthermoelectric cooling circuitry for temperature stabilization and ofelectronic circuitry for exposure control and pulsewidth generation.Maintenance needs are minimal, with a 5000+ hour life on the sourcesequating to several years of use. This low maintenance featurerecommends the technology to the busy surgical suite.

Individual diode elements have limited output power capability and beamshapes which are not amenable to ease of delivery to distant sites.Recent efforts have concentrated on beam shaping and combination ofbeams from a plurality of single elements. Each single element candeliver up to 1 Watt of CW power.

As a consequence, by means of the combination of beams from many suchelements on diode bars, it is now possible to deliver tens of watts ofdiode laser light through flexible fiber optical cable to a distantsite. These high power levels as recently demonstrated by otherinventors (up to 100 Watts) have made possible the new treatment conceptoutlined previously, in which such a source, appropriately modified, maybe used for the current application.

A number of medical device companies have packaged diode laser systemsfor medical use, based on the above OEM subcomponents. Use of theirfinished systems is advocated for urology, gynecology, general andplastic surgery, gastroenterology and ENT. None of these applicationsare directly vascular in nature. Some ophthalmic applications have alsobeen studied in which small retinal vessels were treated with a lowerpower (up to 1.3 Watts) diode laser. It has been shown that smallvessels (<200 um) could be coagulated, but that optimal use would entailthe use of an adjunctive sensitizer dye such as indocyanine green.Larger vessels were not studied. No direct vascular use of the diodelaser in Dermatology has been studied at this time.

Diode laser systems as described above have been utilized for generalsurgical applications on soft tissue, whereby a non-specific cuttingaction results from the delivery of long pulses of light (>100milliseconds pulse widths are typically available from the devices),with power levels in the range 10-60 Watts. In this mode, such a deviceacts as an optical scalpel, with some associated coagulative potential.

One embodiment of the invention involves the modification of such asystem by means of electronic control circuitry to obtain shorterpulsewidth (1-99 millisecond) operation for specific use in selectivedermatological surgery. Such an embodiment may be further modified bythe optimization of the internal semiconductor array design for pulsedoperation and for higher power density focusing of the light. This maybe achieved by judicious coating of the individual diode facets andcloser placement of the diode elements within the array than is typicalin an array optimized for Continuous Wave operation. A higher powerdensity may thereby be realized from the array.

The practice of the invention harnesses the specific targeting potentialof the device by means of a careful control and administration of theparameters as modeled previously. By this means, light is to passthrough overlying tissue, affecting only the desired target vessels.

Direct targeting of large blood vessels on the legs with a high power(˜10-500 Watts) and short pulsewidth diode source has never previouslybeen reported.

The invention consists of a clinical treatment methodology for theeradication of unwanted leg vessels, described in the next section.Pigmented lesions of the skin may be similarly treated, and require theuse of shorted pulsewidth. The treatment method employs modifiedspecific optical apparatus which is described in this section in termsof preferred and alternative embodiments. The combination of parametersdescribed below under `preferred specification` have not so far beenreported in Dermatology and may not have been used in any other medicalspecialty.

One preferred specification for the device is listed below:

    ______________________________________    Host material:                GaAs semiconductor laser source    wavelength range:                800-850 nm    pulsewidth: 1-99 milliseconds    power level:                10-300 Watt, 1 Watt increments    repetition rate:                1-20 Hz.    spot size on skin:                0.5-10 mm, variable    delivery system:                fiber, with dermatology handpiece termination    laser cooling method:                thermoelectric    pulsing method:                electrical    aiming beam:                red diode or helium neon laser (1-10 mW)    tissue cooling:                optional, may be required for 1-3 millisecond                pulses    ______________________________________

This preferred embodiment can specifically be utilized for the treatmentof leg vessels and may also find application in the treatment of facialtelangiectasia, pigment removal and other Dermatological conditionsrequiring high selectivity.

A second embodiment utilizes a commercial scanner to simulate a largerspot size or cover a larger treatment area with greater uniformity. Thisscanner would replace the standard handpiece and would serve tocontiguously place treatment spots on the skin. This would allow for theuse of a smaller incident spot size with consequent higher powerdensity, yet still permit the treatment of large vessels up to 3 mm.Alternatively, this would allow for the rapid uniform coverage of largetreatment areas with any particular spot size. Scan area would rangefrom as little as 2 mm² to as much as 10 000 mm².

A third alternative embodiment employs the use of a contrasting dye suchas Indocyanine Green, which enhances absorption in the preferredwavelength region. This would be injected into the patient prior totreatment with the diode laser, in order to enhance the selectivity ofthe laser action.

A fourth alternative embodiment utilizes a different semiconductormaterial variant producing a wavelength in the range 850-1000 nm, with apower level in the range 10-500 Watts.

A fifth alternative embodiment utilizes a second host material `pumped`by the diode laser. This host material, which itself would then lase ata different wavelength, might consist of a polymer encapsulated dyematerial, or some other glass or crystal structure doped with lasingions.

All of the envisaged embodiments produce near infra-red light with pulsewidths and power levels amenable to the treatment of the targeted legvessels as calculated previously.

This first preferred embodiment is sketched as figure 7:

In practice, a separate foot switch (not shown) provides triggering tothe laser source found within the laser head cabinetry (1). The sourceconsists of a set of arrays of individual laser diodes. Light from thesediodes is typically collected in a series of individual small diameterfibers constituting a bundle. This bundle is grouped together physicallywithin the cabinetry enclosure and light coupled via a high efficiencyconnector into a single larger diameter fiber. An external connector (4)provides an interface to an external length of optical fiber or lightguide (5). This optical delivery media is then coupled into a handpiece(6) containing focusing lenses. These lenses, together with a distancegauge (7), provide precise positioning and laser beam placement onto thepatient's skin (8). The beam at the treatment site may be focused or maybe converging, to achieve a better penetration within the tissue. Powerlevel, repetition rate, and pulsewidth of the source are controlled bymeans of the electronic controls (2) which together provide access tothe specification set listed previously. Displays (3) permitverification of the selected parameter set.

An incorporated visible `aiming beam`, within the cabinetry enclosure,also delivered through the light guide, provides verification of theultimate placement of the invisible treatment laser spot. An audibletone sounds when the short pulses are being administered to provide thephysician with additional feedback.

An optional external cooling apparatus may be employed when short pulses(1-3 milliseconds) are being used for the treatment of vascular lesions.This would employ the application of a chilled media which would reduceepidermal temperature by up to 20° C. to lower its damage threshold.

Clinical Treatment Methodology

The goal of the treatment is to lighten and eventually clear the vesselwhile leaving the surrounding normal skin intact and unaffected. Belowis presented an optimal and novel therapeutic treatment methodologysuitable for use in a variety of different clinical applications.

Dermatological applications and uses:

(i) Telangiectasia of the legs

(ii) Mature vascular lesions of the head and neck, including Port winestains and telangiectasia

(ii) Epidermal and dermal pigment removal

A number of major advantages and conveniences are provided by thepresent treatment method, including:

1. The present methodology envisages the use of a specific parameter setchosen to provide optimum selectivity of damage to the target tissueonly. The epidermis and peri-vascular dermis are spared while damage isadministered, in a controlled fashion, uniformly throughout the targetedvessels or pigmented structures.

2. The vessels are uniformly coagulated rather than mechanicallyruptured. This means that blood does not leak out of the vessels intothe surrounding tissue. This leakage is responsible for the gross, andpersistent, purpura and hyperpigmentation which is cosmeticallytroublesome to the patient. The present invention should minimize theserisks.

3. The invention provides for the use of narrow-band coherent infra-redlight. Such light is able to penetrate deep into the dermis with minimalscattering or competitive absorption and affect most of the visiblevasculature.

4. The equipment used to provide the therapy can be manufactured atrelatively low cost and has great ease of portability. This willultimately result in greater patient access to the therapy.

5. The procedure is relatively gentle and painless, and obviates the useof multiple needle injections as associated, for instance, withsclerotherapy.

6. Several treatments are required. Each treatment will provide anoccasion for the physician to tailor the parameters to the individualneeds of the patient. Hence, the personal health, safety and cosmeticappearance of the skin are affected only to the extent required, and anyside effects minimized.

7. Minimal damage is caused to surrounding skin structures, which do notabsorb well at the near- infra- red wavelengths. Water absorption islow, minimizing peri-vascular direct heating, and epidermal heating islow, minimizing epidermal pigmentary change and epidermal disruption.This is turn minimizes any complications associated with woundformation.

General treatment procedures and preferred details:

Vessels with size in the range 0.1-3.0 mm will respond best totreatment. Vessels with a powerful deep feeder vein are least likely torespond to treatment by any available method.

A power level in the range 10-500 Watts is used, with 40-50 Watts beinga `typical` value for a small associated spot size of 1 mm. Larger spotsizes up to 10 mm will require higher power. A Pulsewidth in the rangeof 1-99 milliseconds will be used, with smaller vessels requiringsomewhat shorter exposure pulse widths. Use of the shortest pulse widths(1-3 milliseconds) may require the adjunctive cooling of the epidermis.A wavelength in the range 800-850 nm is preferred due to itsinsensitivity to blood oxygenation. This removes an important variablefrom clinical consideration.

After treatment, the site may be somewhat blanched (whitened) due tosome coagulation of tissue. Some fine purpura may also be present, as aresult of the intra-vascular coagulated blood or vasculitis associatedwith vascular swelling.

Compression may be applied to the site pursuant to treatment to minimizethe potential of the body to `re-grow` the endothelial cell structuresdefining the vessels.

An assessment will be made at the second visit relating to any color ortexture change of the skin. The vessel itself will also be graded forany lightening. Absence of any lightening or adverse effects will betaken as indicative of the need to increase energy or exposure time.

Occurrence of significant adverse sequellae will be taken as indicativeof the need to decrease power and exposure parameters.

Detailed Protocol

The vessel group to be treated is photographed under controlledconditions and its diameter measured using a slide scale or needle. Itis further examined to detect the presence of scarring or otherwiseabnormal color or texture.

The site of treatment is first shaved, to remove obstructive absorbinghairs.

Individual vessels are designated as test sites to which differentcarefully chosen parameters of laser light are applied. An initial setof parameters for smaller vessels.

(0.1-0.5 mm) might be: 40-50 Watts of light, 1 mm spot size, 3-20millisecond exposure time. Larger vessels may respond better to somewhatlonger pulse widths and may best be treated with larger spot size. Thismay in turn require the use of higher power up to 500 Watts. Severalsuch spots would be placed linearly along one of the vessels comprisingthe test site. Different vessels within the group are exposed withincreasing power levels or pulse durations. Increases may be in steps of5 Watts and 3-5 milliseconds. Feedback is obtained from each applicationin terms of immediate tissue response and used to determine subsequenttest site parameters. Desired response includes a whitening of thevessel without abnormal texture or damage to the overlying tissue. Somereddening of the treated area is also desirable, which is associatedwith the inflammatory (erythemic) response of the body.

Following treatment, a topical antibiotic ointment may be applied to thetreated site and the skin area covered with a dressing. This dressing,or a separate structure, may also be used to achieve localizedcompression and restriction of blood flow.

The patient will return after a specified healing period (usually 2-16weeks) for evaluation and further treatment. These additional treatments(typically up to 5) will be administered with the parameters found toinduce optimal vessel lightening with minimal adverse sequellae.Parameters will be adjusted if the response is inadequate.

(insufficient lightening) or too severe (induration, ulceration orpigmentary change to the overlying epidermis). In the former case,applied power and/or pulsewidth will be increased, while in the latter adecrease will be effected.

If a vessel does not respond after a total of 6 treatments, treatmentshould be discontinued. This is likely to be indicative of the presenceof a high pressure underlying feeder vein system, or some othercombination of adverse mechanical or biological characteristics. In anyevent, the patient should be followed for up to one year to note anyincidence of recurrence.

It is claimed:
 1. A therapeutic skin treatment device for the removal ofunwanted leg veins and other vascular and pigmented lesions from theskin of a human, the device, comprising:a laser head containing powersource, laser source, controls, and cooling electronics; an opticalfiber connector and light guide optically coupled to the laser head forreceiving light produced by the laser head; an optical scanner forsimulating a larger tissue spot size, a focusing optics element, and adistance gauge for distance control of tissue contact, connected to theoptical fiber; and a control circuitry element electronically connectedto and controlling generation of a plurality of pulsed coherent lightwith a wavelength in the range of 700-1000 nm, a power level in therange of 20-60 Watts, and a pulsewidth in the range of 30-99milliseconds for effecting partial conduction in the surrounding dermis.2. A therapeutic skin treatment device for the removal of unwanted legveins and other vascular and pigmented lesions from the skin of a human,the device, comprising:a laser head containing power source, lasersource, controls, and cooling electronics; an optical fiber connectorand light guide optically coupled to the laser head for receiving lightproduced by the laser head; a dermatology handpiece connected to theoptical fiber, said dermatology handpiece comprising an optical scannerfor uniformly irradiating a larger tissue area a focusing opticselement, and a distance gauge for distance control of tissue contact;and a control circuitry element electronically connected to andcontrolling generation of a pulsed coherent light with a wavelength inthe range of 700-1000 nm, a power level in the range of 20-60 Watts, anda pulsewidth in the range of 30-99 milliseconds for effecting partialconduction in the surrounding dermis.
 3. A therapeutic skin treatmentdevice for the removal of unwanted leg veins and other vascular andpigmented lesions from the skin of a human, the device, comprising:alaser head containing power source, laser source, controls, and coolingelectronics; an optical fiber connector and light guide opticallycoupled to the laser head for receiving light produced by the laserhead; an optical scanner for simulating a larger tissue spot size, afocusing optics element, and a distance gauge for distance control oftissue contact, connected to the optical fiber; and a control circuitryelement electronically connected to and controlling generation of aplurality of pulsed coherent light with a wavelength in the range of700-1000 nm, a power level of at least 20 Watts, and a pulsewidth of atleast 30 milliseconds for effecting partial conduction in thesurrounding dermis.
 4. A therapeutic skin treatment device for theremoval of unwanted leg veins and other vascular and pigmented lesionsfrom the skin of a human, the device, comprising:a laser head containingpower source, laser source, controls, and cooling electronics; anoptical fiber connector and light guide optically coupled to the laserhead for receiving light produce by the laser head; a dermatologyhandpiece connected to the optical fiber, said dermatology handpiececomprising an optical scanner for uniformly irradiating a larger tissuearea, a focusing optics element, and a distance gauge for distancecontrol of tissue contact; and a control circuitry elementelectronically connected to and controlling generation of a pulsedcoherent light with a wavelength in the range of 700-1000 nm, a powerlevel of at least 20 Watts, and a pulsewidth of at least 30 millisecondsfor effecting partial conduction in the surrounding dermis.